Power hammer



Feb. 3, 1942. 5. D. BEHLEN 2,271,933

' POWER I HAMMER I Filed April 25, 1940 3 Sheets-Sheet 1 BY M'Xm ATTORNEY Feb. 3, 1942. K e. D. B'EHLEN 3 3 POWER HAMMER Filed April 25,1940 3 Sheets-Sheet 3 INVENTUR Z110 BY W Ximrz,

- ATIQRNEY Patented Feb. 3, 1942 UNITED STATES PATENT O FFICE POWER. HAMMER George D. Behlen, Chicago, I11. I

Application April 25, 1940, Serial No. 331,609

6 Claims. (01. 125-33) My invention relates to power driven hammers.

My invention has particular reference to the type of hammer which may be driven by either a flexible shaft or a rigid shaft. In the construction of a power driven hammer which may strike from 400 blows per minute'up to 2,500,

' depending upon the size and capacity of the.

hammer, it is well known that each blow produces a corresponding reaction which must be controlled in order to prevent self-destruction of the hammer.

It has been known heretofore that the reaction from each striking blow of the hammer element may be dissipated back through the drive shaft, however, this is undesirable because of the deleterious effect upon the drive shaft and its associated parts. It has also been known to dissipate the reaction through the walls of the housing. This is also undesirable because of the deleterious effect upon the working part of the'tool and upon the operator.

The primary object of my invention is to control this reaction, not by dissipating it, but by utilizing it for energizing each successive blow of the hammer element. In this way I not only control the undesirable deleterious effect of the reaction, but, instead, I transform said reaction into useful working energy.

Another object of my invention is to increase the work output of each blow of the hammer element without increasing the work input. The important aspect of increasing the work output of the hammer without increasing the work input is emphasized by the commercial demand for a mechanical hammer which will compete withthe well known pneumatic hammers.

A further object is to provide a cushioning means'for the tool holder so as to reduce to a minimum the injurious consequences which result from operating the hammer without putting it to work.

A further object is to provide a convenient device for starting and stopping the hammer.

Another object is to provide a readily demountable housing cover which has a special bearing platefor preventing axial movement of the hammer element on its pivot.

Another object is to provide a special coil spring for energizing the working blow of the hammer element in which the tension exerted by the spring on the hammer element is equalized from end to end of the spring.

Another object is to control the releasing of the energy conserved by the coil spring so that the maximum benefit of said energy is imparted by the hammer element to the tool holder Which receives the blow of the hammer element.

Other objects and advantages will be apparent upon reading the following description and upon examination of the drawings, in which: Fig. 1 is a sectional view through one side of the hammer;

Fig. 2 is a sectional View taken on line 22 of Fig. 1; r

Fig. 3 is a fragmentary sectional view similar to Fig. 1 but showing the hammer element in a difierent location within the housing;

Fig. 4 is a perspective of the hammer element alone;

Fig. 5 is a front View partly in section of the tool holder alone; and

Fig. 6 is a view of the spring alone.

In the preferred embodiment of my invention I have shown generally a housing A having a handle B formed integrally therewith, a hammer element 0 which'revolves and strikes the tool holder D upon each revolution, and a tool E to which is transmitted each blow of the hammer element upon the tool holder. I

The housing A is formed of an elongated portion 2 and a laterallyextending portion 3 defining a chamber Within which the hammer element C is adapted to rotate. A drive shaft, preferably flexible, (not shown) is adapted to be received in the elongated portion 2 of the housing. A suitable clutch (not shown) is also provided within the elongated portion of the housing in order that the operation of the hammer can be controlled from the handle B. The clutch is controlled by means of a pair of diametrically opposed studs 6 (only one of which is shown)which extend into the interior of the elongated portion 2 of the housing, through the elongated slots 1 in the housing wall. The studs are operatively connected to the clutch and movement of the studs in one direction along the elongatedslots 1 causes engagement of the clutch and movement in the other direction causes disengagement.

The operation of the clutch is controlled by a manipulating lever 8 which is mounted within the hollow handle. The lever pivots about the pin 9 which extends transversely of the handle and is securely held inthe bosses l0 which are formed integrally with the walls of the handle. Either end of the lever is free to move up and down within the cutaway portions II and I2 in the handle. Pivoted to one end of the lever 8 by means of pin [3 is a connecting rod I4 which extends between the lever and the bracket l5. Bracket I5 is pivoted to a lug it which is formed integrally with the housing A. The studs 6 are secured to the bracket l5 and move therewith. The studs 6, as heretofore described, control the engagement and disengagement of the clutch. Thus when the operator presses down on the lip portion H of the lever 8 this causes the clutch to engage and starts the hammer to operate. A releasing of the downward pressure on the lip I! causes the clutch to disengage and the hammer to stop operating. Thus it can be seen that the hammer can be operated from the handle of the tool, even though the source of power may be remote therefrom.

Referring to Fig. 2 a flexible shaft (not shown) may be received in the elongated portion 2 of the housing A and may be securely attached thereto in the threaded region l9. A stub shaft is operatively connected to the clutch and flexible shaft and is driven by said flexible shaft. The stub shaft 20 is rotatably journaled in bearings 21 and 22 and is formed at one end with a head 23. Disposed eccentrically of the axis of said stub shaft and preferably formed integrally therewith is a pin 24 extending across the interior of the housing. One end of the hammer element C is bifurcated and each limb of the bifurcation has a cylindrical bore 25 therein which is axially aligned with the bore of the other limb. The bifurcated end of the hammer element C is adapted to slidably fit onto the eccentric pin 24 so as to be free to pivot about said pin. The free end of the pin 24 terminates in the plane defined by the exterior surface of the side wall of the hammer element which is adjacent the housing cover 25. The housing cover prevents the hammer element from sliding axially along the pin 24. The clearance between the side wall of the housing cover and. the adjacent side Wall of the hammer element is only sufficient to allow freedom of rotation of the hammer element. The housing cover has a special bronze insert 21 which is molded as part of the casting from which the housing cover 25 is formed. This insert serves as a bearing plate to limit axial movement of the hammer element. It can be seen that the hammer element and the spring 28 can be quickly replaced by removing the housing cover and sliding the hammer element off the pin 24.

The spring 28 is a special type of coil spring and is adapted to slidably fit onto the pin .24. The spring 28 is formed by coiling one end clockwise and the other end counter-clockwise as viewed in Fig. 6. By forming the spring in this manner each end of the spring has an outwardly extending stem 29 and 29a. and midway between the ends of the spring is a U-shaped tongue 30 extending outwardly at a tangent to the coils of the spring. The stems 29 and 29a lie in a common plane and are also tangent to the spring coils the reason for which will presently appear.

The spring 28 is received in the recess defined by the bifurcated end of the hammer element and is journaled. on the pin 24 as previously described. The stems 29 and 29a of the spring are adapted to abut against the shoulder 32 which forms the base of the bifurcated region of the hammer element. The U-shaped tongue portion of the spring is adapted to abut against a pin 33 which is preferably formed integrally with the stub shaft '20 and extends outwardly therefrom. The spring normally tends to urge the hammer element in blow striking direction. The tension exshoulder.

Referring to Figs. 1 and 3 the laterally extending portion 3 of the housing A defines a chamber within which the hammer element is adapted to rotate. This chamber consists of a region 34 having a radial dimension which is greater than the radial dimension of the remaining region 35 of the chamber. In the region 35 a bronze bearing plate 36 is fixedly mounted to the inner wall of the housing. At the point where the reduced region 35 meets the enlarged region 34 a step-off 3'! is formed. When, upon rotation, the hammer element is passing through the region 35 of the chamber, it engages the bronze bearing plate 36 and when it passes through the enlarged region 34, it clears the wall of the housing. The exterior surface of the blow-striking end of the hammer element is rounded off at 36a to conform substantially to the arc defined by the inner surface of the bearing plate 36 so that the hammer element will ride smoothly against the bearing plate.

Formed integrally with the housing portion '2 and extending downwardly as a continuation thereof is a cylinder 38 having a sleeve 39 fixedly journaled therein. The sleeve 39 serves as a bearing for the tool holder D which is reciprocably mounted therein. The tool holder is provided with an axial bore 4| in its upper region which opens into a second and diametrically larger axial bore '42 which in turn opens into the lower end of the tool holder. The bore 42 is adapted to slidably receive the butt end of the tool or chisel E. A hardened tip 43 is pressed into the lower end of the bore 4| for transmitting the blow of the hammer element to the butt of the chisel The tool holder D is provided with a transverse slot 44 through which a pin 45 is journaled. The walls of the cylinder 38 are provided with diametrically opposed openings 45 through which the pin 45 is inserted. The pin 45 remains in a fixed position when inserted into the openings 45 and its function is to limit the reciprocative movement of the tool holder D and also to prevent the tool holder from falling out of the cylinder 3B. Journaled in the bore 4| is a compression spring 41 which contacts with the pin 45 and normally urges the tool holder u-pwardly toward the hammer element. The function of the spring is to provide a cushioning means for the tool holder whenever the hammer is operated without the chisel E being applied to the work. It can be seen that when the chisel is being pressed against the work, there is a constant upward pressure on the tool holder which returns the tool holder into operative position for each succeeding blow of the hammer element. However, when the chisel is not being applied to the Work and if there were no spring 41., then there would be nothing to urge the tool holder upwardly into position for succeeding blows of the hammer element and consequently the tendency would be for the hammer element to drive the tool-holder out of the housing.

At the upper end of the tool holder there is a head portion 48 adapted to receive the blow of the hammer element. The head portion 48 has a slide-way which comprises in its upper region a convex surface 49 and in its lower region a concentric mass.

cave surface 50. Y Theconcave region 50 defines an are which corresponds with the arc defined by the bearing plate 36. Thus it can be seen In order to avoid'unnecessary vibration due to the eccentricity of the hammer element relative to the axis of the drive shaft I may provide 'addi-' tional weight for the head 23 diametrically opposite the pin 24so as to counterbalance the co- Operation V The hammer is operated by "first pressing downwardly on the lip H of lever B which establishes a driving connection between the powersoUrce and the hammer element. The hammer element is thus. caused to rotate in acounterclockwise direction asindicated in Figs. 1 and '3. Immediately after the hammer element has struck the head of the tool. holder 'it'rebounds backwardly in a clockwise direction about its pivot, (pin 24). It can be seen that by mounting the hammer element so that it is freely pivotal relative to the drive shaft, the reaction upon the drive shaft is negligible. During the backward anti-clockwise movement of the hammer element the spring 28 is caused to coil as shown in Fig. 3. Each additional unit of distance that the hammer element moves in rebound direction increases the opposing tension of the spring until the resistance of the spring equals the force of rebound movement, then rebound movement ceases. It is apparent that the energy which is present in the rebound movement of the hammer element is absorbed by the spring 28 which conserves this energy for future use. gy is not wasted or dissipated through extraneous channels. a

At the moment when the rebound movement of the hammer element reaches its limit, the continued rotation of the drive shaft has caused the eccentric pin 24 to assume the approximate position shown in Fig. 3. Consequently the position ofv the head of the hammer element relative to the head of the tool holder remains substantially unchanged during the period of rebound movement and upon the continued rotation of the drive shaft the head of the hammer element slides into contact with the'bearing plate 36 without any undue jar to the housing wall. This desired condition of operation depends upon regulation of the size, capacity and resiliency of the spring 28. j r

During the period of rotation when the hammer element is riding along the bearing plate 36, the spring 28 retains its conserved energy. When the head of the hammer element reaches head: of "thehammer element engages thev tool holder. Thusit'canbe seen that]; have provided 'a hammerwhich-produces a p'owerfulblowJin proportion to its'size, weight and'motive power.

claim i is:

a drive shaft associated therewith, a hammer ele- 'of the hammer element to catch up to" its normal position, therebyincreasing the momentum of the hammer element, said increase'dimomening that this additional blow-striking. energy, imparted to the hammer element; by both the spring 28 and by the catching upof the hammer element, reaches itspeak at the momentthe Having thus described my invention 1 what I 1."A percussive device comprising a housing,

a drive shaft associated therewith; a hammer element adapted to be rotated bysaid drive'shaft, a tool holder slidably mounted for limited reing means within the tool holder for absorbing the blows or the hammer element uponithe ltool holder when the percussive device is being operated without being put to work, said cushioning means comprising a spring mounted in a bore within the tool holder. T

2. A percussive device comprisingsa housing,

ment adapted to be rotated by said drive shaft, a tool holder slidably mounted for limited reciprocal movement relative to the housing and extending into the interior forreceiving the blows of the hammer element, said tool holder having a transverse slot, a pin journaled through the slot for allowing the limited reciprocal move- The enerthe step-01f 3'! this conserved energy is released, U

thereby increasing the blow-striking energy of the hammer element.

In addition to this increased working energy supplied by the spring 28 there is a still further source of increased working energy imparted to the hammer element. During the period of rotation in which the hammer element is passing the bearing plate 36, the head of the hammer element is caused to lag behind its normal position, which is the position determined by drawing a radial line through the axes of the eccentric pin 24 and the drive shaft 20. When the head of th hammer element reaches the stepoff 31, centrifugal force tends to cause the head ment of the tool holder, and cushioning means located within-the tool holder for absorbing the blows of the hammer element upon the tool holder when the percussive device is being operated without being put to work, said cushioning means comprising a spring mounted in a bore within the tool holder.

3. A percussive device comprising a housing, a drive shaft. associated therewith, a hammer element adapted to be rotated by said drive shaft, a tool holder slidably mounted for limited reciprocal movement relative to the housing and extending into the interior thereof for receiving the blows of the hammer element, said tool holder having a transverse slot, a pin journaled member, a stop member extending outwardly from the carrier, a spring associated with the carrier and with the hammer element, whereby movement of the hammer element about the pivot member in rebound direction is resiliently resisted by the spring, said spring having a connection with the stop member and also the hammer element, said stop member being located relative to the pivot member, so as to permitthe hammer element to move in rebound direction from the position of the hammer element the moment it strikes; the anvil, means within the housing to cause the hammer element to lag behind its normal position, and other means for releasing the hammer element so as to allow said element to catch up to'its normal position, thereby increasing the force of the blow of the hammer element on the anvil.

' '5. A percussive tool comprising ahousing, an anvil, a rotatable hammer element carrier, means for rotating said carrier, a pivotmember extending from the carrier and located eccentrically x01 the :axis of said carrier, said hammer element mounted for freeswinging movement on the pivot member, a spring associated with the carrier and with the hammer element whereby movement of the hammer element about the pivot member in rebound direction is resiliently resisted by the spring, cmeanstwithin the housing to cause the hammer element to lag behind its normal position, said means also serving to energize and to store blow-striking energy in the spring, and other means for releasing the hammer element so as to allow said hammer element to catch up throughout an arc :of more than 120, measured to .itsenormal position, said last means also serving to release the :energy stored in the spring.

*6. A percussive tool comprising a housing, an anvil, arotatable hammer element carrier, means for rotating said carrier, a pivot member extending from the carrier and located eccentrically of the axis of said carrier, said hammer celement mounted for free swinging vmovement on the .pivot member, a spring having connection with the 'carrier'and with the hammer element whereby movement of the hammer element in rebound direction is resiliently resisted by the spring, a cam track within the housing located in the path of rotation of the hammer element whereby said element is caused to lag behind its normal position and whereby the spring is energized, said energization being maintained throughout the extent of the cam track, the lagging condition of the hammer element and the energy stored in the spring being released when the hammer element reaches the end of the cam track, whereby maximum blow-striking force is imparted to the hammer element the moment it strikes the anvil.

GEORGE D. BEHLEN. 

